Tweak compaction candidate selection to avoid keeping page with low occupancy around.

src/debug.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1886 matching lines @@
     Handle<Code> lazy_compile =
         Handle<Code>(isolate_->builtins()->builtin(Builtins::kLazyCompile));
 
     // Keep the list of activated functions in a handlified list as it
     // is used both in GC and non-GC code.
     List<Handle<JSFunction> > active_functions(100);
 
     {
       // We are going to iterate heap to find all functions without
       // debug break slots.
-      isolate_->heap()->CollectAllGarbage(Heap::kMakeHeapIterableMask);
+      isolate_->heap()->CollectAllGarbage(Heap::kMakeHeapIterableMask,
+                                          "preparing for breakpoints");
 
       // Ensure no GC in this scope as we are going to use gc_metadata
       // field in the Code object to mark active functions.
       AssertNoAllocation no_allocation;
 
       Object* active_code_marker = isolate_->heap()->the_hole_value();
 
       CollectActiveFunctionsFromThread(isolate_,
                                        isolate_->thread_local_top(),
                                        &active_functions,
@@ skipping 305 matching lines @@
 
 
 void Debug::CreateScriptCache() {
   Heap* heap = isolate_->heap();
   HandleScope scope(isolate_);
 
   // Perform two GCs to get rid of all unreferenced scripts. The first GC gets
   // rid of all the cached script wrappers and the second gets rid of the
   // scripts which are no longer referenced.  The second also sweeps precisely,
   // which saves us doing yet another GC to make the heap iterable.
-  heap->CollectAllGarbage(Heap::kNoGCFlags);
-  heap->CollectAllGarbage(Heap::kMakeHeapIterableMask);
+  heap->CollectAllGarbage(Heap::kNoGCFlags, "Debug::CreateScriptCache");
+  heap->CollectAllGarbage(Heap::kMakeHeapIterableMask,
+                          "Debug::CreateScriptCache");
 
   ASSERT(script_cache_ == NULL);
   script_cache_ = new ScriptCache();
 
   // Scan heap for Script objects.
   int count = 0;
   HeapIterator iterator;
   AssertNoAllocation no_allocation;
 
   for (HeapObject* obj = iterator.next(); obj != NULL; obj = iterator.next()) {
@@ skipping 29 matching lines @@
   }
 
   // If the script cache is not active just return an empty array.
   ASSERT(script_cache_ != NULL);
   if (script_cache_ == NULL) {
     isolate_->factory()->NewFixedArray(0);
   }
 
   // Perform GC to get unreferenced scripts evicted from the cache before
   // returning the content.
-  isolate_->heap()->CollectAllGarbage(Heap::kNoGCFlags);
+  isolate_->heap()->CollectAllGarbage(Heap::kNoGCFlags,
+                                      "Debug::GetLoadedScripts");
 
   // Get the scripts from the cache.
   return script_cache_->GetScripts();
 }
 
 
 void Debug::AfterGarbageCollection() {
   // Generate events for collected scripts.
   if (script_cache_ != NULL) {
     script_cache_->ProcessCollectedScripts();
@@ skipping 1257 matching lines @@
     {
       Locker locker;
       Isolate::Current()->debugger()->CallMessageDispatchHandler();
     }
   }
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal